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Guided Bone Regeneration Using an Allograft Material

Review and Case Presentations

Monish Bhola, DDS, MSD

Bone grafts have long been employed for the treatment and correction of periodontal defects and ridge deficiencies. The rationale behind bone graft use originates from the osteogenic, osteoinductive, or osseoconductive properties possessed by the grafting materials.1 Osteogenic material stimulates new bone formation, as bone-forming cells are contained within the graft itself. Osteoinductive materials stimulate bone formation in the surrounding tissue immediately adjacent to the graft. In contrast, osseoconductive materials serve as scaffolds for bone growth within existing bony walls.2

Sources of bone grafts include autografts, allografts, xenografts, and alloplasts. Autografts are obtained from extra- or intraoral sites and implanted in the same patient from whom they are obtained. Although the use of autografts often results in the redevelopment of periodontal attachment, significant morbidity is associated with their placement, including ankylosis and root resorption.3 Xenografts contain tissues transferred from one species to another and synthetic alloplasts have been used in grafting applications as well. Allografts were developed using materials harvested from cadavers of the same species to circumvent the morbidity associated with autogenous bone grafts.4 Application of allografts elicited minimal postoperative pain and clinical signs of immunologic rejection.

Cells derived from periodontal ligaments and bones have the potential to heal by true regeneration.5 The process of guided bone regeneration (GBR) regenerates lost alveolar bone and promotes hard tissue formation by employing a barrier. It is used to regenerate bone in preparation for implant site development. As techniques evolved, predictable intraoral GBR was developed for localized ridge augmentation and repair of dehiscences, or tissue ruptures, around implants.6,7

Guided bone regeneration is also used to correct bony defects (eg, fenestrations, dehiscence defects) around dental implants. Researchers have concluded that GBR is a predictable treatment for dental implants placed in sites with insufficient bone structure.8

In comparing resorbable and nonresorbable membranes, there is no evidence from available randomized clinical trials supporting superior success with one or the other.9 However, bioabsorbable collagen membranes may simplify the surgical technique and make it more predictable.

Case Presentations

In this case series, an allograft with osteoinductive properties was used with a GBR resorbable collagen membrane.

Case 1

A 62-year-old female patient with controlled hypertension presented with pain and exudate from a non-healing scar in the mandibular left central incisor region. This tooth exhibited signs of failed endodontic treatment or a possible root fracture. A non-healed incision line (from endodontic surgery) was present on the facial aspect of tooth #24 (Figure 1). During surgery, the incision line was refined, and a full-thickness flap was reflected. A vertical root fracture was present and the tooth was extracted, at which time an extensive facial dehiscence was noted. The area was augmented with an allograft and a collagen barrier was placed over the graft material without the aid of tacks or sutures (Figures 2 and 3). The facial flap was periosteally released to attain tension-free primary closure. The surgical site was sutured with 5-0 vicryl sutures, which were removed at the two-week postoperative visit. Upon surgical re-entry at six months, adequate bone volume was present and a 3.3 mm × 10 mm implant was placed (Figures 4-5-6-7).

Case 2

A 22-year-old male patient with an unremarkable medical history presented with a vertical root fracture to his maxillary left first central incisor as a result of sports-related injury (Figures 8 and 9). The tooth was atraumatically extracted, and an extensive facial fenestration was observed (Figures 10 and 11). The area was augmented with an allograft and a collagen membrane was placed on the facial and occlusal aspect of the extraction socket, extending underneath the palatal gingiva. The facial flap was repositioned and no attempt was made to attain primary closure. The site was sutured with 5-0 Vicryl sutures, which were removed at two weeks. The patient was instructed to clean the area with a chlorhexidine mouthrinse and cotton swabs for a period of six weeks. At six weeks, the epithelialization of the extraction site was complete. Upon surgical re-entry at six months, sufficient bone volume was present, and a 3.3 mm × 12 mm implant was placed (Figures 12 and 13).

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Case 3

A 64-year-old female patient with an unremarkable medical history presented with pain in relation to the maxillary left central incisor. Clinical examination and a radiograph revealed the presence of a large post in tooth #9 and an area of periapical radiolucency (Figure 14). The tooth was extracted, and the socket was augmented with an allograft. A collagen membrane was placed on the occlusal aspect of the extraction socket, extending beneath the facial and palatal gingiva. A figure eight 4-0 Vicryl suture was placed to keep the membrane secure. The suture was removed at two weeks. Sufficient ridge width was present at the six-month assessment (Figure 15). Upon surgical re-entry, sufficient bone was present and a 3.3 mm × 12 mm implant was placed (Figures 16 and 17). The implant was then restored six months post placement (Figures 18-19-20).

Discussion

Clinical Considerations

Guided bone regeneration is a predictable means of restoring lost osseous tissue, resulting in successful implant survival.10 Although autogenous block grafts have been employed in GBR, there is associated neurological and vascular risk with their use.7 The use of allograft materials may minimize such risks. A premixed paste of demineralized bone matrix and mineralized cancellous chips, blended with a reverse-phase resorbable medium, is an ideal material as it easily flows to fill the defect and its viscosity reduces risk of dislodgement when placed. In addition to the bone allograft, the authors applied a collagen resorbable membrane to the site in each of these cases. This application may have served an advantage over the use of nonresorbable membranes, since the latter may exhibit wound-line opening and infection due to bacterial colonization, thus jeopardizing the results of the regeneration.11

Case Selection

Bone volume is a significant predetermining factor that must be considered prior to implant placement. Careful selection criteria and clinical, as well as radiographic, evaluation is a prerequisite for proper treatment planning. The primary selection criteria included cases with alveolar ridge deformity or deficient bony walls at the time of extraction. Site preparation was completed to obtain sufficient bone for future implant placement. Furthermore, patients should be evaluated for any possible allergies to the grafting materials. To help ensure biocompatibility, allograft material was treated with polymyxin B sulfate, bacitracin, gentamicin, and iodine. Patients were assessed to ensure no possible allergic reactions to these materials prior to initiating treatment.

Indications and Contraindications

Guided bone regeneration is an invasive procedure and exhibits indications and contraindications as would any other treatment modality. The main indication for GBR includes an overall healthy patient with no pathologies present within the bony defect. It is generally believed that the standard implant length should be approximately 10 mm, in order to ensure the most predictable and favorable survival rates.12 Bone augmentation may be necessary to obtain sufficient bone volume for better implant survival.

Contraindications may include a medical condition that is not well controlled (ie, uncontrolled diabetes mellitus, cardiovascular disease, immunocompromising conditions, severe degenerative bone disease), a heavy smoking habit (ie, > 20 cigarettes per day), or pathology, localized active infection, deformity, or radiation therapy to the site to be augmented. Such conditions will predispose patients to postsurgical complications (eg, graft mass infection, loss of the augmented bone).

Conclusion

As the presented surgical cases demonstrate, guided bone regeneration enhanced the preservation of hard and soft tissue contour. There was no infection or surgical complication present and predictable bone regeneration was obtained and verified at time of surgical re-entry. This allowed for good implant positioning as well as improved aesthetic and functional results. Overall, GBR using an allograft paste demonstrated no adverse effects on clinical implant osseointegration and sufficient periodontal health was observed in all the cases.

*University of Detroit, School of Dentistry, Department of Periodontology and Dental Hygiene, Detroit, Michigan.